This research constitutes the first phase of a program designed to create a fully automatic, implantable drug-delivery system to control dangerously high blood pressure. The system consists of a novel blood pressure sensing system, an electronic processor, and a drug-delivery system. The first phase of research will determine the applicability of the new blood pressure sensing system which does not require direct contact with the bloodstream and does not include a pressure transducer. This system exploits the well-known dependence of arterial pulse wave velocity upon blood pressure and the consequent decrease in pulse transit time with increasing blood pressure. The arterial pulse will be detected by continuously measuring the change in electrical impedance that appears between a bipolar electrode placed alongside an artery. By using two pairs of electrodes alongside any artery at different distances from the heart, pulse transit line, which is inversely related to blood pressure, can be obtained without contact with the bloodstream. The proposed research will examine the feasibility of using these two concepts to measure continuously the arterial pressure as well as the feasibility of using the impedance pulse transit time to control blood pressure in the anesthetized, experimental animal.